Canadian police are investigating whether a telephone threat to a Pakistani jet which forced a diversion to Sweden was a hoax.
The Canadian authorities were contacted by a woman on Saturday claiming that a passenger was carrying explosives.
Passengers were taken off the plane in Sweden and a man was detained for questioning before being released.
The plane resumed its flight and has now arrived safely in Karachi.
Canadian police say they received two anonymous phone calls from a woman who contacted them from within Canada.
She gave few details in her first call, police say, but in the second one she said a man on board was carrying explosives with the intention of blowing up the aircraft.
The Pakistan International Airlines plane, a Boeing 777, was carrying more than 270 people when it was diverted to Arlanda airport near Stockholm.
Police used sniffer dogs to search the plane, but no explosives were found.
Swedish police detained a man described as a Canadian of Pakistani origin in his 30s.
He was later released without charge and allowed to leave Sweden, prosecutors said. However, the plane departed on Saturday afternoon before he was released. Police said he would receive help to reach his destination.
The plane flew on to the English city of Manchester, where a fresh crew took over the controls before continuing on to Karachi.
If the call was a hoax, the caller could be charged with public mischief, the Royal Canadian Mounted Police said.
